Load control and scheduling are two key functions to manage the radio resources in wideband code division multiple access (WCDMA) systems. The scheduler distributes the radio resource among user equipments (UEs) while the load control estimates the available scheduling headroom that the scheduler may use. This is illustrated in FIG. 2, which shows the prior art procedure of scheduling. The uplink load control provides the Enhanced uplink (EUL) scheduler with the total scheduling headroom for a cell. The scheduler selects the user equipment(s) to be scheduled and distributes the available scheduling headroom among the selected user equipment(s) (step 20). The scheduler then maps the scheduling headroom to power offset or enhanced transport format combination (E-TFC) for each UE to be scheduled (step 21). The scheduler then signals the scheduling grants in terms of maximum E-TFC or power offset to the UEs via a scheduling grant signalling (step 22). The UEs select a suitable E-TFC below the granted E-TFC (step 23). The radio base station (RBS) measures the cell rise over thermal (ROT) and carrier-to-interference ratio (CIR) and inputs the measurements to the uplink load control, which adjusts the maximum scheduling headroom based on the received measurements (step 24) and provides the scheduler with this adjusted scheduling headroom, and so on.
In the uplink, the common radio resource shared among the user terminals is the total amount of tolerable interference, which is defined as the average interference over all the antennae. A relative measure of total interference is rise over thermal (ROT), i.e. the total interference relative to thermal noise.
Load factor represents the portion of uplink interference that a certain channel of a certain user terminal generates, which is defined as the interference due to the channel of that user terminal divided by the total interference. The total load factor of different channels equals to the sum of load factors due to different channels.
The uplink load control estimates the resource utilization in terms of cell load generated by different type of traffic and channels of each cell based on measurements, such as, rise over thermal and CIR; the load control also regulates the maximum available scheduling headroom that the scheduler can use to schedule user equipments for transmitting data in the cell.
The scheduler distributes the available scheduling headroom among the user equipments which have data to transmit, either one at a time, time division multiplexing (TDM) scheme, or several at a time, code division multiplexing (CDM) scheme. The scheduler determines when a certain user equipment is allowed to transmit and at what maximum data rate. In the existing scheduling framework, two scheduling grants, absolute grants and relative grants are used to control data transmission limit of each user equipment. The data transmission limit is expressed in terms of the maximum E-TFC. The E-TFC for different data rate is formulated by power offset between the enhanced dedicated physical data channel (E-DPDCH) and dedicated physical control channel (DPCCH), as shown in equation (1):pwroffgrant—estk=f(loadavik,loadDPCCH—estk,loadsched—estk)  (1)wherein:                pwroffgrant—estk is the (estimated) maximum power offset that can be granted for user k;        loadavik is the available scheduling headroom for user k;        loadDPCCH—estk is the (estimated) DPCCH load from user k; and,        loadsched—estk is the (estimated) load from the channel(s) that are already scheduled for user k.        
The scheduler signals the scheduled user equipment with the maximum E-TFC or the maximum power offset via scheduling grant. To determine the scheduling grants, the uplink load generated by each scheduled user equipment needs to be estimated.
The uplink load may be estimated based on carrier-to-interference ratio (CIR) measurements. Suppose user k has N uplink channels, the load generated by the user equipment can be calculated by equation (2):
                              Load          i_est          k                =                                            CIR                              1                ⁢                _meas                            k                        ·                          pwroff              i_est              k                                                          loadpar              1                        +                                          loadpar                2                            ·                              CIR                                  1                  ⁢                  _meas                                k                            ·                              (                                  1                  +                                                            ∑                                              i                        =                        2                                            N                                        ⁢                                          pwroff                      i_est                      k                                                                      )                                                                        (        2        )            wherein:                CIR1—meask is the (measured) CIR of the 1st channel from user k;        pwroffi—estk is the (estimated) power offset between the ith channel and the first channel of user k;        loadpar1 is the first load estimation parameter; and,        loadpar2 is the second load estimation parameter.        
The load parameters are system parameters selected by the radio network controller (RNC).
In the existing solution the scheduler controls the user equipment data rate by limiting the maximum E-TFC. To estimate the maximum E-TFC for a user equipment, the load generated by each user equipment in the cell needs to be estimated. There are several problems for EUL scheduler to estimate the load in the previously known systems:                Due to the inner-loop power control, the DPCCH power used by a user equipment may vary quite a lot from the time when the EUL scheduler estimates the load to the time when the grant is used by the user equipment;        The load generated by the granted E-TFC can be completely different from the load that was estimated at EUL scheduler;        Another difficulty for EUL scheduler is to take into account individual receiver type of EUL user equipments when the load of a granted E-TFC is estimated, since the impact of self-interference is not negligible.        
The inaccuracy in the load estimation causes large oscillations in the actual cell load or rise over thermal; To ensure stability of the system, a large load margin is introduced to prevent the instability. However, it is difficult to configure the load margin for all different scenarios. A conservative large load margin may result in inefficiently utilization of resource while a small load margin may cause large oscillations in rise over thermal, both have negative impact on the system throughput.
The addressed problems may be mitigated by:                Dynamically adapting the load parameters according to the temporary radio environment.        Power based load estimation (according to the original definition of load factor), where the load factor due to the ist channel of user k is estimated as:        
                              Load          i_est          k                =                              pwr            i_meas            k                                Itot            meas                                              (        3        )                            The variation in radio environment, etc. is automatically reflected in the wide band received power. This is because the uplink (inner loop) power control always tries to adjust the user equipment power so that the perceived CIR at the base station is close to the CIR target. The level of received power will however, depend on the receiver scheme, data rate and radio environment.        Introducing another inner power control loop to control the total received power. This inherently avoids oscillation in rise over thermal even with fixed load parameters.        
However, for all the schemes a precondition to achieve evident performance gain (both increased throughput and decreased rise over thermal oscillation) is that system delay is small and scheduling as well as load estimation are performed sufficiently frequently (especially when with high target rise over thermal). This is because with large system delay the load may vary a lot from the time when the EUL scheduler determines the power offset (E-TFC) that can be granted to the time when the granted E-TFC is used by the user equipment. This may lead to distinct load estimation error at the time the grant is used by the user equipment, even though the load is accurately estimated at the time the EUL scheduler issues the grants. Thus, the benefits of these schemes are decreased.
On the other hand, decreasing system delay is not an easy task when signaling procedure is involved, and more frequent execution of scheduling implies higher signaling overhead, especially for the third alternative addressed above, where two power control loops are needed.